By Matt Peckham
We are so living in the future. A group of scientists from Scotland and the Czech Republic says it’s managed to drag around teeny-tiny objects using nothing more than a beam of light.
That’s essentially how it worked when the crew of the starship Enterprise periodically unleashed its tractor beam to tug derelict vessels (and once even the captain himself, snared by an interstellar disco-light show). Unfortunately, the no-longer-science-fiction light beam is currently limited to yanking around microscopic matter.
How’d they do it? According to Phys.org, researchers at the University of St. Andrews in Scotland and the Institute of Scientific Instruments in the Czech Republic figured out a way to reverse what’s known as the “radiation pressure” of light — that is, the actual force exerted by electromagnetic radiation on matter.
Shine a light source at something and the photons in the beam exert a force on the object. It’s minuscule force — if we’re talking about a flashlight pointed at a refrigerator, forget about it — but examine what’s happening at microscopic levels and you find those photons are acting on objects in quantifiable ways. In fact an MIT graduate student recently proposed using this force as a way to deflect Earth-threatening asteroids by bombing them with clouds of white paint (think “cosmic paintball gun”); because brighter colors reflect more light than darker ones, the sun’s photons can — over the course of many, many years — gradually nudge the asteroid into a non-lethal trajectory.
Imagine that force operating in reverse and you have a sense for how this micro-scale “tractor beam” works: A laser beamed through a lens strikes a mirror, causing it to fire back and across the oncoming beam in a vaguely X-like configuration. The photons in the reflected beam then interfere with the oncoming one, ultimately shoving the particles of matter being “tractored” backwards.
So how long before we’re running around with gravity guns, Half-Life 2 style? Probably never: According to study lead Dr. Tomas Cizmar, the light particles still transfer energy to the object — scale up the laser’s power, in other words, and you’ve just turned your innocuous ultra-cool tractor beam into an ultra-fiery death ray.